Abstract
This paper models the residual stress distributions within micro-fabricated bimorph cantilevers of varying thickness. A contact model is introduced to calculate the influence of contact on the residual stress following a heat treatment process. An analytical modeling approach is adopted to characterize bimorph cantilevers composed of thin Au films deposited on thick poly-silicon or silicon-dioxide beams. A thermal elastic–plastic finite element model (FEM) is utilized to calculate the residual stress distribution across the cantilever cross-section and to determine the beam tip deflection following heat treatment. The influences of the beam material and thickness on the residual stress distribution and tip deflections are thoroughly investigated. The numerical results indicate that a larger beam thickness leads to a greater residual stress difference at the interface between the beam and the film. The residual stress established in the poly-silicon cantilever is greater than that induced in the silicon-dioxide cantilever. The results confirm the ability of the developed thermal elastic–plastic finite element contact model to predict the residual stress distributions within micro-fabricated cantilever structures with high accuracy. As such, the proposed model makes a valuable contribution to the development of micro-cantilevers for sensor and actuator applications.
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Abbreviations
- MEMS:
-
micro-electro-mechanical-systems
- t 1 :
-
film thickness
- t 2 :
-
beam thickness
- δ1 :
-
displacement of film
- δ2 :
-
displacement of beam
- ΔT :
-
temperature rise
- α1 :
-
thermal expansion coefficient of film
- α2 :
-
thermal expansion coefficient of beam
- θ:
-
slope
- ν:
-
deflection
- σ x :
-
residual stress distribution
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Acknowledgements
The authors would like to thank the financial support provided by the National Science Council in Taiwan (NSC 93-2218-E-212-011).
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Lee, CY., Tsai, CH., Chen, LW. et al. Elastic–plastic modeling of heat-treated bimorph micro-cantilevers. Microsyst Technol 12, 979–986 (2006). https://doi.org/10.1007/s00542-006-0115-1
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DOI: https://doi.org/10.1007/s00542-006-0115-1